The present invention relates to systems for transporting particulate materials, and more particularly to a system for feeding such particles from a hopper.
A number of schemes for agitating particles in a hopper are known for promoting flow from the hopper. However, many of these degrade the particles, particularly where the particles are fragile and there is a need to preserve their original form. Such is the case in blasting for surface treatment of a workpiece when it is important to keep the particles sharply defined as to form and size.
In an important class of systems for transporting particulates, pellets or particulates of a hygroscopic or deliquescent material are used, often in a very cold or frozen condition. Excessive agitation of this class of particulates is undesirable because of the resultant wear and pulverization of the particles. The heating associated with the agitation is also undesirable. Also, the incorporation of thermal insulation in the design of the hopper is made more difficult by the presence of agitator components. Further, the introduction of air into the hopper should be minimized for avoiding deleterious heat and/or moisture exchange with the pellets.
A further consideration in particulate feeders is that it may be required that the particles be fed gradually. A disadvantage of some feeders is that they clog at low to moderate feed rates.
Thus there is a need for a particulate delivery system that effectively and reliably feeds the material, even at low and moderate flow rates, while avoiding the other disadvantages of the prior art.